Solar eclipse. Artwork showing the mechanics of a solar eclipse. During a solar eclipse, the Earth passes into the shadow of the Moon, which appears to block the Sun. The Moon's shadow comprises a dark central umbra surrounded by the lighter penumbra. A total eclipse is only visible from within the umbra. From an area covered by the penumbra, a partial eclipse is visible. A total solar eclipse can only occur at New Moon, when the Moon lies directly between the Earth and the Sun. It does not occur every New Moon as the orbital planes of the Earth and Moon are slightly inclined with respect to each other.